Immunohistochemical detection of factor IX and collagen IV in human popliteal artery.

Frozen sections of fresh tissue were stained with polyclonal antisera to factor IX (f.IX), factor X (f.X), collagen IV, or preimmune rabbit serum (control). In each panel, the endothelial (lumenal) surface of the vessel faces the label. Note the primary localization of red staining to the endothelial surface for the factor IX and collagen IV panels. Some faint staining is also present in the subendothelium and media. By contrast, only faint staining in the media is seen for factor X. Original magnification, 400×.